UV to near-IR obser vãtions of the DART-Dimorphos collision

The impact of the Double Asteroid Redirection Test (DART) spacecraft with Dimorphosãllows us to studyãsteroid collision physics, including momentum transfer, the ejecta properties,ãnd the visibility of such events in the Solar system. We report observations of the DART impact in the ultraviolet (UV), visible light,ãnd near -infrared (IR) wa velengths. The observations support the existence ofãt least two separate components of the ejecta:ã fastãndã slow component. The fast-ejecta component is composed ofã gaseous phase, movingãtãbout 1.6 km s -1 withã mass of ≲10 4 kg. The fast ejecta is detected in the UVãnd visible light, but not in the near-IR z-band observations. Fittingã simplified optical thickness model to these observationsãllows us to constrain some of the properties of the fast ejecta, including its scattering efficiencyãnd the opacity of the gas. The slow ejecta component is movingãt typical velocities of up toãbout 10 m s -1 . It is composed of micrometer-size particles, that haveã scattering efficiency,ãt the direction of the observer, of the order of 10 -3ãndã total mass of ∼10 6 kg. The larger particles in the slow ejecta, whose size is bound to be in the range between ∼1 mmãnd ∼1 m, likely haveã scattering efficiency larger than that of the pre-impact Didymos system.